Abstract This study is a longitudinal examination of children (ages 4 ? 10 at initiation) adopted from the child welfare system to determine those factors that influence more adaptive post-adoption development, particularly in the critical capacity of self-regulation. A primary goal of this study is to evaluate the formative influence of factors in the home, specifically the parent-child relationship and pet ownership. The specific aims are: (1) In a sample of 285 children adopted from the child welfare system, test the hypothesis that pet ownership is related to the child's concurrent self-regulation abilities and parent-child relationship when assessed within a year of the adoption. in a sample of 300 children adopted from the child welfare system, test the hypothesis that pet ownership is related to the child's concurrent relationship with a primary caregiver at Time 1, (2) test the hypothesis that pet ownership, including quality of relationship with a pet, at Time 1 positively influences growth in self-regulation and parent-child relationship as assessed 12 months after Time 1 (i.e., Time 2), and (3) examine whether associations identified in Aims 1 and 2 are moderated by identified candidate moderators, such as the age or gender of the child, the child's length of time in the home, and the number and species of pets in the home. Assessment procedures are multi-method and multi-reporter and include objective report questionnaires, performance-based tasks, interviews, structured direct observations, diurnal cortisol patterns, and psychophysiological assessment via an electrocardiogram. The research questions developed and the assessment strategy employed are derived from attachment theory and a developmental psychopathology framework to allow integration of the findings into the larger corpus of developmental research. Data will be collected from children and parents across the commonwealth of Pennsylvania and recruitment will occur in partnership with the commonwealth's office of Children and Youth Services. All data collection will be done in the families' homes to improve participation and retention, as well as to gain a better understanding of the home-life of the families. Results of this study will inform future research on the role of pets in child development as well as provide recommendations on how to improve outcomes for children adopted from the child welfare system.